This invention relates to ozone-based water purification systems. More particularly, this invention relates to water purification systems utilizing vertical counterflow tubes wherein water flow is alternately directed up and down through the tubes. In addition, static mixers may be fitted within the tubes to generate turbulence therein.
Commonly known ozone water purification systems comprise the elements of an ozone gas generating apparatus, a water carrying tube including an ozone contact time segment, and a bubble separating column or chamber. The ozone generating apparatus typically comprises a cylindrical chamber through which atmospheric air containing diatomic oxygen is pumped or drawn. Radiation from a lamp capable of emitting intense ultraviolet light having a wavelength of approximately 185 nanometers excites the diatomic oxygen within the chamber. As a result of such molecular excitation, a fraction of the diatomic oxygen within the chamber is split, producing free atoms of oxygen. As a result of their extremely high chemical reactivity, free oxygen atoms within the chamber rapidly react with the remaining intact oxygen, forming molecules having three atoms of oxygen. Molecules consisting of three oxygen atoms are commonly referred to as ozone, which exists naturally as a gas.
Another commonly known method of producing ozone gas within a chamber is to introduce closely spaced electrodes therein and to induce a sufficient electrical potential difference between the electrodes to produce electric discharge arcing. Diatomic oxygen molecules in close proximity with such electrical arcing similarly degrade into free oxygen atoms, which quickly react with diatomic oxygen to form ozone gas.
In commonly known configurations of ozone water purification systems, ozone-rich air emitted from the ozone generator apparatus is introduced into a stream of water in need of purification, such water typically moving through a tube. Where the air within the ozone-generating apparatus is pressurized by, for example, an air compressor, the output of the ozone generator may be introduced into the water-carrying tube by means of a simple air line interlinking the output of the ozone generator and an aperture extending through the wall of the water-carrying tube. Alternately, the air line may terminate at a venturi installed in line with the tube creating a localized venturi effect at the output end of the air line. Use of a venturi allows the kinetic energy of water within the water-carrying tube to perform work upon the air within the air line, drawing air through the ozone generator via the air line and into the stream of water.
Ozone carrying air which is either injected into the contaminated water stream or drawn into the stream by a venturi initially exists in the form of air bubbles. In order for the ozone gas to have a purifying effect upon the water, such gas must be dissolved into the water. Such dissolving of the gas into the water necessarily occurs at the spherical surface tension boundaries between the gas and the water. A high solubility differential between common air components and ozone gas causes the ozone within such air bubbles to dissolve more quickly than other gases. An exception to this occurs where an ozone residual exists in water in close proximity to the bubbles. Here, rate of infusion of ozone into the water may be reduced due to the strong negative charge of the ozone molecules. In any case, ozone carrying bubbles must remain immersed in water a sufficient length of time to achieve sufficient dissolution of ozone.
In commonly configured ozone water purification systems, the water-carrying tube serves dual functions, both transporting water containing dissolved ozone to its desired destination, and providing an elongated immersion chamber where air bubbles containing ozone may remain in contact with the water for a sufficient length of time to allow dispersion of the ozone into the water. In order for ozone dispersion to occur within the water-carrying tube, the tube must have a sufficient length, i.e., an ozone contact time length. The contact length of the tube may typically be between approximately 1-4 feet or so in length. However, the length may vary depending upon variables such as rate of flow within the tube, turbulence and water temperature. Sharp turns within the tube or turbulence-inducing baffles or screens installed within the bore of the water carrying tube may serve the function of breaking larger ozone-carrying bubbles into smaller bubbles, increasing the overall surface area of the bubbles, and increasing the rate the ozone dissolves into the water. In addition, where an ozone residual exists in water proximate the bubbles, transfer of ozone from the bubbles is inhibited. While venturi injectors or mixers such as those used in dissolving ozone into water provide a small bubble size, the flow of water just downstream the injector, within 12-15 inches or so, becomes laminar. As such, the bubbles, being entrained in a laminar flow just downstream the injector, become so closely packed together that they merge into larger bubbles. Further, the fluid moving with the bubbles in the laminar flow becomes permeated with ozone, inhibiting further transfer of ozone from the bubbles.
Where water bearing dissolved ozone gas is poured into a body of water such as, for example, a swimming pool, the ozone beneficially reacts with various contaminants. For example, ozone rapidly reacts with metal ions within the water, forming precipitants which may be removed through filtration. Ozone dissolved in water also degenerates or causes lysis of the cell walls of bacteria, killing bacteria, viruses and protozoan organisms. However, while ozone kills bacteria and viruses almost instantly, protozoa such as those that harbor the bacteria that cause Legionnaires disease require longer exposure to higher concentrations of ozone to be killed. Ozone within water also beneficially oxidizes and neutralizes sulfides, nitrates, cyanides, detergents, and pesticides. In all such cases, the efficacy of ozone in reacting with such contaminants is enhanced by reducing the physical distance between contaminant organisms or molecules and the molecules of ozone within the water. In a large volume of water, such as a drinking water storage tank, spa, or swimming pool, the concentration of dissolved ozone becomes undesirably low, slowing the rate at which the ozone reacts with contaminants. To prevent such dilution of ozone concentration, it is desirable to first introduce the ozone-carrying water into a reaction chamber having a smaller interior volume which maintains higher concentrations of ozone.
Accordingly, it is an object of the present invention to provide an ozone-based water purification system which incorporates in series an ozone generating apparatus and an ozone contact tubing segment, the contact segment configured as vertical tubes so that water flows alternately upwardly and downwardly in the tubes.
It is another object of the invention to provide such an ozone-based water purification system wherein turbulence and mixing of the flow of water and bubbles is induced in the contact tubing segment. This keeps bubble size small, and does not allow a buildup of ozone in water proximate the bubbles, allowing more ozone to dissipate into the water. In addition, this mixing and turbulence enhances killing of bacteria and viral organisms by disturbing the laminar flow within the contact tubing segment.
Other objects and benefits of the present invention will become known to those skilled in the art upon review of the detailed description which follows, and upon review of the appended drawings.